Automatic rerecording method and system



AUTOMATIC REREGORDING METHOD AND SYSTEM Filed Avril 22. 1944 2 Sheets-Sheet l f Recorder- Amp/171 19 ws 38% E E k w: R} NA 1 'G/AQLES 0. 527M520;

' INVENTOR ATTORNEY.

June 11, 1946. c. o. SLYFIELD AUTOMATIC RERECORDING METHOD AND SYSTEM Filed April 22,, 1944 2 Sheets-Sheet 2 Patented June 11, 1948 AUTOMATIC RERECORDING METHOD AND SYSTEM o Charles 0. Slyfleld, 'Los Angeles, Calif., assignor to Radio Corporation of Americana corporatlon of Delaware Application April 22, 1944, Serial No. 532,256

This invention relates to motion picture sound opnuratus and particularly to a'rerecording system wherein a plurality of sound records are comblood into a. composite sound record.

In the production of sound motion pictures, it is well known that the picture are usually photographed on one film and the dialogue 'is usually recorded on a separate film. Also, on additional films, there may be recorded background noises or sound elifects', such as hoof beats, crowd noises, etc... as well as music. The sound effect records may have been recorded prior to the particular picture being mode and he in the form of loops which are reproduced simultaneously with the dialogue, music, and other records. During the rercoording process, the volume of the various separate trucks or records are varied in the propor proportion to make u sinsle complete record which has the dramatic ed'cct.

For instance, in the recording of a dance or storm scene, it is desirable to have the background music and storm noises decrease in volume during a conversation or other dialogue, and this has been accomplished in. the post by either having the mirror manually reduce the volrune of the music during the dialogue sequences or by having the dialogue signal automatically reduce the comic or effects level. A system of the latter type disclosed and claimed in Mueller Patents lfidd/Edl of November 22, 1932, and 2,075,861 of April d, l93'l. In such an automatic system,

11 Claims. (on. iro -100.3)

constructed control track prepared for a portionlar sound track or picture Control track systems for varying the reproduced volume of a signal are well-known, on such type or system being disclosed in Burrill PatentNo. 2,270,260, of

January 2d, 1942. This patented system employs a variable area control track on the film intermediate the sprocket perforations. A reproducing system employing c, control traclr having a constant frequency and varying amplitude is disclosed in Weinberger Patent No. 1,850,701, of March 22, 1932, while a control track rerecordlng system using c, constant frequency and varicble proper timing, balance, and

the timing" and reduction of the volume is solely dependent upon the dialogue signal. .Thus, if

i there were pauses between words or between-sentenses, the level of music or other background sounds would actually rise during such periods. It has been loin the background signal at a predetermined low level during an entire dialogue sequence recordless of the length of the pauses therein. It hos also been found preferable in order to obtain the proper relationship between the increases end decreases in the different'signals, to have the background sounds begin to diminish prior to the beginning oi the dialogue and to begin to lode hack prior to the end of the dialogue seduences. With an automatic system controlled found desirable, however, to main-- by the dialogue signs! only, or with manual con troi, these results cannot be accomplished in the unilorm manner desired. l i

The-present invention, therefore, is directed .to a system which is automatic to the extent that the level of the music or other sound effectsis reduced in accordance with a specialtype of preamplitude tone is disclosed and claimed in Wolfe Patent No. 2,279,018, of April '1', 1942. The present invention, however, is directed to a control track. having a. constant amplitude and constant frequency.

From the above, it is .opparent-thot various types of control trucks may he used for controlline the volume of a signal truck and that the music or sound effects track may be automatically reduced in volume during the dialogue sequences while rerecording. However, in the present invention, a constant amplitude, constant frequency control track is synchronized and timed in d novel manner with the beginning and end of each dialogue sequence to outometicoliy accomplish it new mixing operation oi a plurality oi tracks "co ing rerecorded. v

The principal object of the invention, there= lore, is to facilitate the rerecording of a, plurdllty of sound records into a single record.

Another object of the invention is to provide an improved rerecording system wherein one sound track is reduced in amplitude during time periods 4 determined by a control track preconstructed'in accordance with the occurrence of the sound sequences on another sound track.

A further object of the invention is to provide an improved method of rerecordlng oplurolity of sound tracks into a singletrcckwhereby the level of one track is automatically controlled with respect to the occurrence of sound sequences on another track. F

A further object oi the invention is to Provide mine the time of reduction and the amount of increase in volume of one record in any desired relationship with respect to the occurrence of the sound sequences on another record. l w

. with respect to a control track, and

oi the automatic system embodying the invention.

Fig. 2 is a diagrammatic view showing the manner of'synchronizing a plurality of sound tracks Fig. 3 is a schematic volume control portion circuit oi the system shown in Referring now to Fig. l, a plurality of reproducing sound lieadsor phonograph are shown at 5, B, l, and 3, reproducer I stant frequency, constant amplitude tone such as 1000 cycles per second, although other frequencies or forms of control tracks may be used, into corresponding electrical currents, while re- Droducers 8 and I translate music and sound effects tracks into respective corresponding electrical currents. Reproducer 8 performs the some function for a dialogue track. Although the invention is described as embodied in a sound film rerecording system, it is to he understood that the rerocording may be from disc records to a disc record, from disc records to 2. him record, or from him records to a disc record. The invention may also be' used in the straight reproduction of sound records. The outputs of the reproducers 5 to 3, inclusive, are shown connected by conductors Ml, ii, 52, and i3 to potentiometers ill, l8, ill, and 38. respectively, mounted on. a mixing console 2E3. These potentiometer-s are for thepurpose otmanually varying the volume oi the electrical cur rent from the output 0! the reproducers" in a well-mourn manner.

After modification by the potentiometer it, the

' control tone is impressed upon a control tone rectifler 22 over conductor 23, the rectified current output being impressed over conductor 2 on a variable gain amplifier 28. In the control'tone circuit, on amplifier may be used intermediate the potentiometer i6 and rectifier 22, or between the potentiometer it and eoundhead a The out- 59 outs of potentiometers lb and l? are combined and then impressed over conductor 28 on the variable gain amplifier 26. The dialogue currents are transmitted over conductor 29 to one of the primaries oi a-transiormer 85-, while the output oftho variable gain amplifier 28 is transmitted overconductor $2 to a second primary oi the transformer 35. The secondary of transformer 3| is connected over conductor 88 to an amplifier 3! which feeds a recorder 8'5 over conductor cc.

For clarity, the elements of Fig. l are shown con-' nected by single conductors.

In the usual rerecordingsystem, the mixer controls the level or the output of each reproduce'r in accordance with a cue sheetthereby-controlling the fading in and out otthe music and back- 7 ground effects. Inthe present invention, the reductlon and increase in volume of the music and sound efiects is under control of a control track,

anoaoos ill quences, while the rate at which the'control track acts upon the background efiect currents is obtained by the timing'of the electrical circuits oi the control track as will now be explained.

Referring now to Fig. 2, a control track is shown at Ml having a start mark 4!, constant frequencyconstant amplitude tone sections 42, and opaque leader sections 43. A dialogue track i shown at $5 with its start marlr 56, its dialogue sections ill, and its opaque leader sections 48. The music traclr i shown at 56 with its start mark 5i, its opaque leader section 52, and its music section 58, while the sound eflects track 55 has a start marl; $5, an opaque section 5%, and asound effects section Eli. The music and sound effects may be continuous over an entire scene, or also made up in section with opaque leader sections in any suitable, manner as is well-known in the art. Furthermore, many pictures requireseveral back ground efiect tracks while others may use only a single traclr in addition to the dialogue track.

the mixer, however, having control of the amount of uniform variation introduced by the control track. The times at which the control track acts on the background eilect currents with respectto placement oithe control track with respect to the occurrence of the various signal track sethe dialogue track current is obtained by the the start marks are all lined up to a tone amplifier.

of the tracks in Fig. 2,

at some predetermined point, such as the reproducing aperture when the films are threaded in their respective reproducer 5, 6, l, and 3; Since the films are then advanced simultaneously at the same ac coloration and speed, the reproduction of each tr l: will occur as shown in Fig. 2. As the are reproduced, the music and sound efiecte some in first before the first dialogue sequence. However, ten frames before each dialogue sequence which, since the dime are advanced at the rate of 2 frame per second, corresponds to slightly From the arrangement less than one-half second, the'control track it begins reducing the gain oi the variable gain amplifier 26 by an amount determined by the setting of potentiometer 5. The control track then ends frames before the ending of each dialogue sequence which corresponds to second. This amount of anticipation has been found to provide a particularly smooth fade out and in of the music and/or sound eflects which is practically unnoticeable by the listener while providing excellent intelligibility oi'the dialogue, since it insures understanding of the first word of each dialogue sequenoe. These results are enhanced by the electrical timing of the control circuit which will now be described in connection with Fi 3.

in Fig. 3 the primary of a transformer 83 be connected toeither the potentiometer l or The secondary oi former Elli is connected to the anodes oi wave rectifier 62, the output oi which is imp? on a timing filter'connistina oi condenser d resistor '36 in parallel. The timing filter is connected to the control amplifier so to: varying cordance with the amplitude of the control signal.

at is, the control tone places a negative bias on the variable gain amplifier 28. thus reducing its gain and correspondingly the level of the musicand/or sound'eflects being transmitted by this amplifier. Various types of may be used, such as disclosed and claimed in Singer Patent No. 2,274,505, or February 24,

As mentioned above, in addition to having the control tone begin reducing the level at the currents corresponding to the background sounds prior to the beginning and to begin increasing the level prior to the end at each dialogue oe= quence, the values of the timing elements 62-33 are so chosen in conjunction with the condenser in the grid circuit of the variable gain amplifier that itrequires 15 frames to fade the background grids of the variable the gain thereof are variable gain systems sounds to any desired predetermined level and 29 frames to fade these sounds back in again. These times correspond to slightly over second and 1 second, respectively, and aid in securing the smooth transition between background and dialogue for high quality recording.

Thus, by placement of the control track sections with respect to the dialogue sequences, the

reduction of the background eiiects level is begunv frames before the beginning of the dialogue to insure understanding the first word of the dialogue, the reduction in level continuing into 5 frames of the dialogue to insure understanding of particularly low level passages in any of the dialogue sequences. By extending the rate of reductionover a period of more than second, there is no distortion introduced in the form of plops or amplitude bumps. By starting the increase in the background sound level :1 frames before the end of each dialogue sequence and timing this action to occur slightly over a period of 1 second duration, there will be no undesirable silence immediately after the dialogue to cause a listener to be aware that the background signal level has been reduced duringthe dialogue sequences.

For the above timing values, the condenser 63 had a value of 0.25 mfd. and the resistor was 250,000 ohms, the transformer 68 was an RCA RT-525, and the rectifier 62 was an RCA 6H6.

. The value of the condenser in grid circuit .of the variable gain amplifier was 0.25 mfd. Although the above timing and the 10 and 4 frame anticlpatory starting has been found preferable in this particular embodiment f the invention, it. is to be understood that other values may be .used since, it is only necessary'to vary the length'of the control tone sections with respect to the length of the dialogue sequences and vary the timing filter constants to provide the action desired.

From the above, it will be noted that the backround sounds will be maintained at a predetermined low safe level as long as the control tone is present, and there will thus be no rise in the music and/or sound effects level during pauses between words or ."entences, regardless of the length of the pauses.

Furthermore, the mixer is able to control the amount of reduction of the back-ground during the rerecording operation by a simple adjustment of a potentiometer on his console which varies the amplitude of the control tone as impressed on the tone rectifier and which remains constant thereafter. The amount of anticipation is obtained by the manner of intercutting the control track constant amplitudeconstant frequency control tone sections, while the rate of rise and fall of the background signal is determined by the values of the timing filter elements. With such a control track system, several reels of control track may be recorded and sections cut therefrom in the lengths required and after use on a particular picture, the sections may be returned to their reels and subsequently recut or spliced to construct control tracks for other sound tracks for subsequent pictures, there thus being no film waste.

I claim as my invention:

1. A rerecording system comprising a plurality of sound reproducers for reproducing a respective plurality of sound tracks, means for amplifying currents generated by said sound tracks, means for manually varying the amplitudes of said currents, a reproducer for reproducing a control track, means for utilizing the currents generated by said control track reproducer for varying the amplitude or the currents generated by at least I rents. 5

6. The method of automatically controlling the one of said sound tracks, and means for manually varying the output from said reproducer of said control track.

2. A rerecording system in accordance with claim 1 in which said control track is a track of constant frequency and constant amplitude.

3. A rerecording system adapted to 'combinea dialogue track with a background effects track. said system comprising a reproducer of said dialogue track, a reproducer of said background effects track, a reproducer of a control track, means for manually controlling the volume of the currents from each of said reproducers, means for combining the currents from said dialogue reproducer and from said background effects reproducer, and means for utilizing the output of claim 3 in which said last mentioned means includes a variable gain amplifier for said background effects currents and a rectifier-filter combination for said control track currents, said rectified currents being impressed on said variable gain amplifier for controlling the gain thereof.

5. The method of automatically controlling the mixing of a plurality of signaltracks by a control track comprising separately translating each of said plurality of signal tracks into respective corresponding electrical currents, simultaneously translating a constant amplitude control track into corresponding electrical currents, and utilizing said control track currents to vary the amplitude of at least one of said plurality of signal currents during the translation of said signal curmixing of a dialogue track and a background effects track by a control track comprising separately translating said dialogue track and said background effects track into respective correspendingv electrical currents, simultaneously translating a constant amplitude control track into corresponding electrical currents, and utilizme said control track currents to vary the amplitude of the background effects currents during the translating of the dialogue sequences.

7. The method in accordance with claim 6 in which said control track becomes efiective to reduce the amplitude of said background eifects currents substantially 10 frames in advance of the translation of said dialogue track into electrical currents and becomes ineffective, substantially 4 frames before the end of the translation of said dialogue track into electrical currents.

8. The method in accordance with claim 6 in which said control track reduces the amplitude of the background effects track from maximum to minimum in approximately one-half second, and increases the. amplitude of said background effects track from minimum to maximum in ap-' proximately one second.

9. The method of anticipating and timing the reduction and increase in amplitude of one signal track with respect to another signal track being combined as a single signal, comprising translating a constant amplitude control track into corresponding electrical currents, utilizing said control track currents to begin the reduction of the amplitude of one signal track approximately %4 of a second in advance of. the beginning of a sound sequence on said other signal track, and

electrically continuing to reduce the amplitude of ing a reproducer for a first signal track, a reproducer for a second signal track, a reproducer for a control track, the signals on said signal tracks being adapted to be mixed into a single signal, and the signal on said control track being adapt- 8 ed to control said mixing, means for utilizing said control track signal for varying the level of said first signal track, said control track being reproduced prior to the reproduction of said second si nal track for beginning the reduction in level of said first signal track in advance of the reproduction of said second signal track, the reproduction of said control track being discontinued prior to the end of said second signal track for beginning theincrease in level of said first signal track in advance of the end of the reproduction of said second signal track, and means included in said last mentioned means for controlling the rate of reduction and increase in level of said first signal track, said reduction from maximum to minimum being at a faster rate than said increase from minimum to maximum.

' CHARLES O. SLYFIELD.

Certificate of Correction Patent No. 2,402,095 June 11, 1946 CHARLES 0. SLYFIELD It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 7, line 4, for the claim reference numeral 11 read .9;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 16th day of May, A. D. 1950.

THOMAS F. MURPHY,

Assistant Uommissz'oner of Patents. 

